Windows are known in the art. For example, conventional IG window units include at least first and second glass substrates (one of which may have a solar control coating on an interior surface thereof) that are coupled to one another via at least one seal(s) or spacer(s). The resulting space or gap between the glass substrates may or may not be filled with gas and/or evacuated to a low pressure in different instances. However, many IG units are required to be tempered. Thermal tempering of the glass substrates for such IG units typically requires heating the glass substrates to temperature(s) of at least about 580 or 600 degrees C. for a sufficient period of time to enable thermal tempering.
Other types of coated articles also require heat treatment (HT) (e.g., tempering, heat bending, and/or heat strengthening) in certain applications. For example and without limitation, glass shower doors, glass table tops, and the like require HT in certain instances.
Diamond-like carbon (DLC) is sometimes known for its scratch resistant properties. For example, different types of DLC are discussed in the following U.S. patents: U.S. Pat. Nos. 6,303,226, 6,303,225, and so forth, which are hereby incorporated herein by reference. It would sometimes be desirable to provide a window unit or other glass article with a protective coating including DLC in order to protect it from scratches and the like. Unfortunately, DLC tends to oxidize and burn off at temperatures of from approximately 350 degrees C. (possibly from 380 to 400 degrees C.) or higher, as the heat treatment is typically conducted in an atmosphere including oxygen. Thus, it will be appreciated that DLC alone as a protective overcoat cannot withstand heat treatments (HT) at the extremely high temperatures described above which are often required in the manufacture of vehicle windows, IG window units, glass table tops, tempered glass articles, and/or the like. Accordingly, DLC cannot be used alone as a coating to be heat treated, because it will oxidize during the heat treatment and substantially disappear as a result of the same (i.e., it will burn off).
Certain other types of scratch resistant materials also are not capable of withstanding heat treatment sufficient for tempering, heat strengthening and/or bending of an underlying glass substrate.
Accordingly, those skilled in the art will appreciate that a need in the art exists for a method of making a scratch resistant coated article that is capable of being heat treated (HT) so that after heat treatment the coated article is still scratch resistant. A need for corresponding coated articles, both heat treated and pre-HT, also exists.
U.S. Patent Document 2006/0057294 (hereby incorporated herein by reference), commonly owned with the instant application, discloses a coated article including a zirconium nitride based layer and optionally a layer comprising DLC. Heat treatment (e.g., thermal tempering) of the coated article causes the zirconium nitride based layer to transform into a scratch resistant zirconium oxide based layer. While heat treated coated articles of the '294 document are good and realize satisfactory results in many instances, there is room for improvement with respect to scratch resistance (SR).